Conventionally, there is known a driving device using a shape memory alloy in the form of a wire, as disclosed in, for example, Japanese Laid-Open Patent Publication Nos. 2000-310181 (see Page 2, FIG. 11) and HEI 5-224136 (see Page 3, FIG. 3). Such a driving device utilizes the characteristics of the shape memory alloy member that changes to a memorized shape when the shape memory alloy member is heated to a temperature higher than a transformation temperature, and returns to its original shape when the shape memory alloy member is cooled to a temperature lower than the transformation temperature. The amount of displacement of the shape memory alloy member is several percents of the entire length of the shape memory alloy member, and therefore it is necessary to increase the entire length of the shape memory alloy member in order to obtain the sufficient output (the amount of displacement) of the driving device. However, if the shape memory alloy member is linearly disposed, it is necessary to provide a large space.
Therefore, a driving device is recently proposed, in which the shape memory alloy member is wound around a winding member so that the shape memory alloy member whose entire length is long can be disposed in a small space. Such a driving device is disclosed in, for example, Japanese Laid-Open Patent Publication Nos. 2000-31018 (see Page 6, FIG. 1), HEI 8-226376 (see Pages 3-5, FIG. 1), HEI 10-148174 (see Pages 2-3, FIG. 1), and HEI 8-77674 (see Page 5, FIG. 5).
However, if the shape memory alloy member is wound around the winding member as disclosed in these publications, the amount of displacement of the shape memory alloy member decreases, compared with the case in which the shape memory alloy member is linearly disposed.